1. Field of the Invention
An apparatus consistent with the present invention relates to a spatial motion recognition system and, more particularly, to a system and method for recognizing motions occurring in space.
2. Description of the Related Art
Recently, the market for personal mobile devices such as personal digital assistants (PDAs), cellular phones, computer notebooks, and so on, has been widely spread. Such personal mobile devices are best suited for ubiquitous environments for utilizing information anytime and anywhere since they are easy to carry. That is, recent mobile devices enable users to utilize information even during their movements so that the users can use information any time and anywhere, unlike the past environments which confined information utilization to desktop personal computers (PCs) installed at a fixed location.
However, such mobile devices have become smaller in an overall size in order to be easily carried, which causes a problem that users feel somewhat awkward or inconvenienced in recognitions and command inputs through a small display unit. In such mobile devices, portability runs counter to being easy to input and output information, so research and development has been continuously made on methods for overcoming these problems.
Recently, a pen-shaped input system has emerged as a means through which users use the mobile devices more conveniently. A general pen-shaped input system is designed to recognize writing motions or selecting motions which are inputted through a tool on the two-dimensional plane or pad so that the pen-shaped input system displays writings on a display unit or performs corresponding operations based on recognized information.
FIG. 1 illustrates an input style for a conventional pen-shaped input system. The pen-shaped input system has a stylus pen part 10 capable of being held in a user's hand so that a user can write or select motions with it, and a display part 22, which may be a PDA 20, for example, that recognizes menu selection commands and/or writing motions from a contact state of a portion of the stylus pen part 10 on the two-dimensional plane of the display part 22 and displays corresponding operations based on a selected menu or handwritings. The pen part 10 operates as a pointing tool or handwriting tool without an extra power supply, and the PDA 20 processes a signal corresponding to a portion of the display part 22 on which the tip portion of the pen part 10 is placed.
The pen-shaped input system described above decides what information is inputted depending upon positions in which the pen part 10 contacts with the two-dimensional plane of the display part 22. That is, if a current view displayed on the display part 22 is a view displaying menus, the PDA 20 decides information corresponding to a position with which the tip portion of the pen part 10 is in contact as menu selection information, and performs a corresponding command based on information on the selected position. Further, if a view capable of recognizing handwritings is displayed, the PDA 20 obtains information on contact positions of the pen part 10 that are continuously changing, and displays on the display part 22 the handwritings from the obtained information.
However, the above pen-shaped input system is inconvenient since users have to perform their menu selections or handwriting motions on the limited view of the display part 22.
Meanwhile, other systems have been proposed for measuring or detecting the coordinate changes of the pen tip in three axial angles outside the pen or through ultrasonic waves or the like, for other types of conventional pen-shaped input systems. Further, there has been proposed a system for detecting the changes of the pen tip used in charge-coupled device (CCD) cameras. For yet other types of conventional pen-shaped input systems, U.S. Pat. No. 6,181,329 (laid-open Jan. 30, 2001) and U.S. Pat. No. 6,212,296 (laid-open Apr. 3, 2001) disclose systems extracting motion information and recognizing input information inside the pen based on motions performed on the two-dimensional plane or in three-dimensional space.
However, problems exist in the systems extracting coordinate changes outside the pen, such as the systems using three axial angles, ultrasonic waves, CCD cameras, and so on, since there is a high possibility of recognition errors if the pen is interfered with by a hand or other object. Further, the pen-shaped input systems disclosed in U.S. Pat. Nos. 6,181,329 and 6,212,296 extract motion information and recognize motions based on pen motions performed on the two dimensional plane or in the three dimensional space, so users can input information without any limit to handwriting space, but, when pen motions occur in the three-dimensional space, there exists a problem that handwritings can be wrongly recovered and displayed differently from users' intents since users can not make handwriting motions precisely on an arbitrary plane in space. For example, as a user performs motions for writing the number “2” as shown in FIG. 2 in space, the positions of points appearing when segmenting the handwriting motions of the number “2” in predetermined time intervals do not exist on any one plane corresponding to each other, so they may appear somewhat compact or as a completely different symbol depending upon recognition directions, which also causes a high possibility of recognition error occurrences. FIG. 3 illustrates a shape of the number “2” based on the handwriting motions of FIG. 1 which appears when viewed in a different direction. Accordingly, the pen-shaped input systems disclosed in the above-mentioned United States Patents can reduce recognition errors when the pen tip contacts the two-dimensional writing surface, but they are not easy to utilize in space.